l-asparaginase encapsulated within erythrocytes (GRASPA((R)) ) should allow serum asparagine depletion over a longer period than the native form of the enzyme, using lower doses and allowing better tolerance. The GRASPALL 2005-01 study, a multicentre randomized controlled trial, investigated three doses of GRASPA((R)) for the duration of asparagine depletion in a phase I/II study in adults and children with acute lymphoblastic leukaemia (ALL) in first relapse. Between February 2006 and April 2008, 18 patients received GRASPA((R)) (50 iu/kg: n = 6,100 iu/kg: n = 6, 150 iu/kg: n = 6) after randomization, and six patients were assigned to the Escherichia coli native l-asparaginase (E. colil-ASNase) control group. GRASPA((R)) was effective at depleting l-asparagine. One single injection of 150 iu/kg of GRASPA((R)) provided similar results to 8 x 10,000 iu/m(2) intravenous injections of E. colil-ASNase. The safety profile of GRASPA((R)) showed a reduction in the number and severity of allergic reactions and a trend towards less coagulation disorders. Other expected adverse events were comparable to those observed with E. colil-ASNase and there was also no difference between the three doses of GRASPA((R)) . (c) 2011 Blackwell Publishing Ltd.